Distribution and life history of the endangered James Spinymussel, pieurobema collina (bivalvia: unionidae)

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Abstract

Distribution of the James spinymussel (Pleurobema collina) and aspects of its life history were
studied from June 1987 to October 1989. Field and laboratory observations were used to determine
gravidity and glochidial release periods, fish host requirements, age class structure, growth characteristics,
and juvenile survival. Stream surveys conducted at 243 sites in 20 counties revealed new
populations of this species in three subdrainages (Catawba Creek, Pedlar River, and Mechums
River), of the James River, greatly expanding its known range.

Female P. collina were gravid from late May through early August 1988 and 1989 in Craig
Creek, Virginia, and the South Fork Potts Creek, West Virginia. Glochidia were released from late
June through early July in the South Fork Potts Creek, at mean water temperatures between 21
and 25 Â°C, and discharges between 0.013 and 0.050 m l/sec.

Juvenile P. collina, fed a mixture of three green algae species in chambers with and without
silt, lived 50 days. Juveniles in silt grew significantly faster than those not in silt after 18 days.
Age and growth characteristics of adults were obtained by thin-sectioning valves collected in
muskrat middens in Dicks and Johns creeks, Virginia. Ages ranged between 3 and 19 yr, and a
strong year class was identified at age 11. Mean annual mortality rate was calculated to be 9.8%.

As judged by qualitative surveys, current populations of P. collina in Craig Creek, Johns
Creek, and the South Fork Potts Creek appear to be self-sustaining. Populations in Catawba and
Patterson creeks appear to be small and are probably in jeopardy of being extirpated. The status
of the James spinymussel in Dicks Creek, Rocky Run, and Pedlar and Mechums rivers is unknown
since these streams were not extensively surveyed.